Answer:
Cost incurred while running a restaurant:
Salary paid = $200,000 per year
Ingredients cost = $50,000 per year
Before running this restaurant, he was earning $150000 per year.
Here, we are using a concept called opportunity cost.
Opportunity cost refers to the benefit of a commodity that is forgone to produce one extra unit of some other commodity.
It is also refers to the value of next best alternative that is given up by choosing some other alternative.
In this question, opportunity cost of running a restaurant is the income that is earned when he was a lawyer, i.e, $1,50,000 per year. This is the income that is foregone when he started running a restaurant.